Abstract:

The interaction between bovine serum albumin(BSA) and five active components of Chinese Herb CⅠ-CⅤ containing structural unit of coumarin was investigated by ultraviolet(UV) and fluorescence spectroscopy(FS). The intrinsic fluorescence of BSA was quenched by pharmaceuticals via forming pharmaceutical-BSA complexes. The quenching mechanism is mainly a combination of static quenching with  nonradiative energy transfer. The parameters of pharmaceutical-BSA binding process, such as statistic quenching constant KP, the apparent association constant KA, the value of binding site n, the efficiency of energy transfer E, the spatial distance r  and ΔG were obtained. The above parameters disclose the structural-performance relationship of pharmaceutical-BSA interaction as follows. The process of pharmaceutical-BSA binding is promoted strongly by both 4-methyl and 6-hydroxyl in coumarin molecule, but the latter must endure simultaneously some adverse effects caused by increment of molecular polarity and stereo hindrance. Decreasing the polarity of 7-substituent group and increasing the volume of substituting group destroys the pharmaceutical-BSA binding, and the effect is almost totally opposite to that of 6-hydroxyl.

Key words: Structural-performance relationship; Chinese Herb; Coumarin; Bovine serum albumin; Fluorescence spectroscopy